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# Vibro acoustic analysis of pump

Experimenter

Hi all!

Merry Christmas！

I have some questions about LMS Virtual Lab Acoustic, which confused me for several weeks.

Now I want to simulate the acoustic field of pump-hydrodynamic machine,

working medium : water

environment : air

pump volute material : steel

the inlet and outlet of pump connects pipes, now in this case I simulate the pump ,alone.

But during my simulation, I meet some questions, so I need some help

If I want to select the Modal Superposition Vibro-acoustic Response Case to calculate the exterior acoustic filed of pump, how to construct the acoustic mesh?

Because the inner fluid material is water and exterior material is air, so I construct two acosutic mesh (as the following picture), the exterior surface of the exterior acoustic mesh is defined as AML Property.

As you can see ,the inlet and outlet of the pump struct mesh are open. I add the inlet and oulet face of the inner acoustic mesh with the Impedence property 1500000 Pa.s/m.

In Acoustic Boundary conditions, I defined Surface Dipole → Vector, the resource from ANSYS-CFX trainsent case, and the face is as following picture.

Coupled Groups : I have Defined two coupled groups,

one is the interface of inner acoustic mesh and struct mesh

one is the interface of exter acoustic mesh and struct mesh

red line is interfacered line is interface (notice the inlet and outlet is open)

So, I don't know if I have defined correct? If it's wrong，how can I do?

# Re: Vibro acoustic analysis of pump

Experimenter

Q2.

As we all known the exterior noise of pump contains two resource:

One is scattering noise from the inner acoustic

One is flow induced vibration radiation noise

So in the simulation, how can I get the true results that contains the two noise?

I have tried the Direct Vibro-acoustic response case , in this case I defined the Acoustic Boundary Condition as Surface DipoleVector, the load face is the envelop face of the inner acoustic mesh,

and I successfully get the results.

But the problem comes, which noise type is this result?

Scattering noise \ flow induced vibration radiation noise or both contains

In other words, what’s the physical meaning of the Direct Vibro-acoustic response case with the Acoustic Boundary Conditions Surface Dipole ?

And how about the Modal Superposition Vibro-acoustic Response Case ?